Audi 4000 Turbo quattro Conversion

The Intro

The Project








Total Bill

Engine Specs

Special Tools

MegaSquirt Install

To start with this part of my web site will be mostly pictorial.  I will try to flush it out with more information as time goes on.  If you have never heard of MegaSquirt it is an open source programmable electronic fuel injection controller.  You have to build it yourself from parts. This takes some time, but is a great option for the low budget do it yourselfer.  Below is a picture of the finished board in the case.  Those with a sharp eye will see one mistake that cost me several hours of troubleshooting on the car before finding it in the ECU.

Like I said it is do it yourself so you also have to make all the wiring.  I got a set of prelabled wires, GM temperature sensors, and GM weather pack connectors from RS Autosport.  If you are not into electronic construction they also sell complete units.  As you can see below the wires are labeled for their function.  It repeats every 4" or so.  It is invaluable.  I made the harness like you see below and then fed it through the existing ECU grommet on the passenger side of the firewall.  It took a great deal of effort since I am still using the ignition system from the KH engine (this version of MegaSquirt does not control spark).  Once I had it fed through I never had to worry about checking which wire was which.  


I laid out all the wire in the engine compartment as needed and zip tied them together in bundles like I wanted.  Then once it was all set I went back and installed split loop protector over all of it removing the zip ties as I went.  I secured the split loop with small wraps of black electrical tape.  I also made a separate harness for the injectors incase I ever choose to change styles in the future.  The finished product with weather pack connectors and split loop protector looks like original equipment (maybe not Audi original, but original).  I also fed through wires for every pin on the MegaSquirt.  This allows for expansion in the future if I choose to add ignition control.

Since the old system used a high pressure continuous injection system I had to make preparations for modern electronic fuel injectors.  The first step is to get all the CIS baggage out of the engine compartment.  Next I installed some 5/16" tube to AN-6 adaptors on the feed and return lines to the tank/pump.  The pictures below show how they go together as well as how they look installed.


In order to control the fuel  pressure we need a regulator.  I chose an aftermarket unit, but I am sure their are cheaper alternatives using OE parts.  The pressure regulator was $135, but once you get the special O-ring AN fittings and a gauge you are closer to $190 so keep that in mind.  In order for the fuel rail to fit height wise and to allow the use of the proper injector O-rings you need to get a set of injector cups from a Golf with Digifant.  The one I looked these up under was a 1990 Golf GL.


Of course you will also need a fuel rail.  I made this at work from rail extrusion.  The rail is about $10/ft.  I think this worked out to about 15 inches of rail.  Be careful since some of the places that sell the material hit you hard on shipping.  Of course this needs more AN fittings to adapt from 3/8" NPT to AN-6.

 For the injector holes I drilled through all the way first with a 1/4" (I think, but exact size is not all that important as long as you don't go to big and the o-ring can't seat against anything) drill bit and then came back with the 17/32" bit for the O-ring seat (look here for common injector dimensions). The ends get pilot drilled 9/16" and then tapped with a 3/8 NPT (pipe) tap.  Make sure you have no burrs from where you drilled.

I don't know if MC engines are the same, but the KH has a bar across the CIS injectors holding them in. This is held down with two bolts to two ears on the valve cover hold down strip. I bent these two ears up slightly and drilled out the nut that is welded to them. Then I installed the rail with the first and last injector only (easier) and marked on the rail with a sharpy marker through the holes I just opened up. I then drilled and tapped for mounting. Mine lined up with the main meat of the rail, but just be careful that you don't drill into the fuel section of the rail when you do this.

Oh yeah I also plugged the air shroud port in the head. I just pulled out the nipple which you can just work out with some pliers and then I tapped it and threaded in a screw with a light coating of RTV. Then I just reinstalled it. If I had the head off I would have been fancier, but I didn't want to risk getting chips in there.

In the spring of 2005 I upgraded MegaSquirt firmware to MegaSquirt'N'Spark - Extra (MS'N'S-E). It adds tons of features, plus it is free!  To start the only added feature I am using is the 12x12 fueling tables (up from 8x8 in the standard code).  The list of features is long including spark, launch, and traction control. The stock distributor off my original JT engine has a 5 window hall sensor that will supply the spark signal MegaSquirt needs to control spark.  Right now however I am working on getting bigger injectors so I can run more boost.  My current injectors are rather tapped out.  Once I get that sorted out I will start running ignition control.

Summer 2005 Update

I have not been driving the car much since it has been fire hot and I have yet to get A/C installed again.  I did recently install 577 cc/min injectors.  They are upgrade injectors for a Dodge SRT.  Thanks Rob!!  Now I can start turning up the boost more and have some fun.  Once I get an EGT sorted out I will look at moving ignition control over to the MegaSquirt.  I have been very slowly working on an exhaust manifold.  I believe I can make a tubular unit that will allow me to reinstall the A/C in the stock locations through the use of some serious heat shielding.  More on that as it progresses.